The present invention relates to a clothing with an action promoting the metabolism of keratin layer and a method for attaching a preferable microcapsule.
Cells composing epidermis are keratinized over maturity because of the accumulation of keratin, so that keratin layer is formed on the surface of skin. Keratin layer is mostly composed of scaly dead cells but is responsible for such an important role for the protection of skin from outside by retaining moisture on skin.
When gets old, a keratin layer is peeled off. Then, a fresh keratin layer is formed on the portion. Bare skin can be retained at a good state by such smooth promotion of the metabolism of keratin layer. When the metabolism of keratin layer is deteriorated due to factors such as aging, stress, nutritional imbalance, and poor care, however, skin gets dry and puffy, causing, for example rough skin, wrinkle and spot.
So as to reduce skin dryness, skin roughness, wrinkle and spot, accordingly, it is most effective to ameliorate the state of keratin hypertrophy involving old keratin layer remaining on skin for a long term and thereby promote the metabolism of keratin layer. So as to resume skin moisture and softness once reduced, further, care is preferably taken on skin so that the metabolism of keratin layer can be promoted and moisture is appropriately retained on skin.
Alternatively, it has been known conventionally that xcex1-hydroxy acids, for example lactic acid, have an action to loosen and soften the binding of old keratin layer densely overlaid together. For example, xcex1-hydroxy acids at a high concentration of about 5 to 20% by weight are used as keratolytic agent for the treatment of callus, verruca and corn and also used as skin peeling agent at beauty salon.
In recent years, additionally, a proposition has been made of a method comprising sealing in a microcapsule a physiologically active substance conventionally used in the forms of external dermal agent and cosmetics and attaching the microcapsule to the fiber of clothing. Such clothing with the physiologically active substance-containing microcapsule attached thereto is intended to perform skin care while the clothing is continuously worn during day-time hours, although skin care has essentially been carried out, mainly before bathing or sleeping by external dermal agents and cosmetics, conventionally.
As one example thereof, Japanese Patent No. 2562233 proposes a fiber structure comprising a microcapsule for fiber-processing agents and a structural fiber to which the microcapsule is attached with a silicone-based or urethane-based resin binder, wherein the microcapsule contains and seals therein at least one substance with an action improving dermal physiological state, as selected from the group consisting of ascorbic acids, tocopherols, sea weed extracts, antipruritics and analgesics and comprises a wall membrane of a synthetic polymer substance and wherein the particle size of the microcapsule is within a range of 2 to 40 xcexcm and the wall membrane is 0.3 to 4 xcexcm thick and the content of the wall membrane is 3 to 60% by weight on a microcapsule weight basis and wherein the weight ratio of the microcapsule and the binder is within a range of 10:1 to 1:5 and the total amount of both the attached microcapsule and binder occupies 0.3 to 15% of the fiber weight in the attached portion.
As to the method for attaching such microcapsule to the fiber of clothing, furthermore, various methods have been proposed conventionally, where the binder types to be added and reaction conditions have been devised and modified. For example, Japanese Patent Publication 80121/1992 proposes, as one example of microcapsule with fragrance, a method for producing a stocking with fragrance, comprising charging a stocking in a process bath containing a microcapsule with fragrance and a silicone-based coating agent in mixture at a weight ratio of 1:1 to 1:2, and subjecting the stocking at a thermal process at 20 to 60xc2x0 C. while the hydrogen ion concentration is preset and retained within a range of 4 to 6 in the process bath by using a buffer.
The method for attaching microcapsule as described in the Japanese Patent Publication No. 80121/1992, for example, specifies the conditions such as hydrogen ion concentration and reaction temperature for enhancing the binding between the microcapsule and the coating agent and between the microcapsule coating agent and the fabric, so as to suppress as much as possible the dissociation of the microcapsule after the attachment, due to washing. However, the method does not pay any consideration to the elevation of the attachment ratio of the microcapsule during adsorption reaction.
According to the method, thus, the amount of the microcapsule charged in a process bath is not equal to the amount of the microcapsule attached to the fiber and the attachment ratio thereof varies with a deviation, depending on the process conditions. From the standpoint of quality control, the method is problematic in that the amount of the microcapsule attached to panty stocking can hardly be retained constant.
Generally, a slight error in the amount of the microcapsule attached is not so problematic in case of a clothing attached with such a fragrance-containing microcapsule as described above. However, it is needless to say that a more strict quality control is demanded for a clothing attached with a microcapsule containing and sealing therein a substance with a physiological action on skin.
Although xcex1-hydroxy acids as natural acids contained in fruit and the like are highly safe, particularly, caution should be taken on the concentration thereof for use. More specifically, some of xcex1-hydroxy acids have been used conventionally at high concentrations of about 5 to 20% by weight as keratolytic agents and peeling agents. For the purpose of gently promoting the metabolism of keratin layer, essentially, xcex1-hydroxy acids are directly coated within a range of 1.5 to 3.0% by weight. At a concentration above the range, human skin sensitive to xcex1-hydroxy acids is potentially irritated.
Furthermore, because the microcapsule described in for example the Japanese Patent No. 2562233 is a decomposable microcapsule containing and sealing therein as the principal ingredient, a thermoset resin for example formalin resin or polyester resin, some of such microcapsules are decomposed under exposure to pressure and friction during fiber processing, prior to product shipping, so that the amount of the microcapsule still holding the effect is decreased by the time when a user wears it, which is problematic from the respect of quality control.
Additionally, the decomposable microcapsule is of a preferable membrane thickness specifically conditioned for gradual decomposition of the microcapsule over wearing. Because the microcapsule is practically at a high decomposition probability at an early stage of use where a larger volume of the microcapsule is attached to portions readily exposed to pressure or friction, the physiologically active substance in the microcapsule is released more at such early stage of use, disadvantageously.
For containing a physiologically active substance such as antipruritic, for which a relatively rapid efficacy is demanded, a decomposable microcapsule can be used, satisfactorily. Because the action of xcex1-hydroxy acids to promote the metabolism of keratin layer requires about one month until the action is exerted effectively as remedies of dry skin and rough skin, the effect preferable can hardly be recovered by using a decomposable microcapsule with a higher release level at an early stage of use.
In such circumstances with the conventional problems, the invention has been achieved. It is a main purpose of the invention to provide a preferable clothing exerting an action to promote the metabolism of keratin layer and overcoming the quality-control problems, and a method for attaching such microcapsule to fiber.
It is an object of the present invention to provide a clothing which overcomes the foregoing problems.
It is a further object of the present invention to provide a clothing having an action promoting the metabolism of keratin layer.
It is another object of the present invention to provide a method for attaching a microcapsule to fiber to give a clothing having an action promoting the metabolism of keratin layer.
So as to attain the purpose, the clothing promoting the metabolism of keratin layer in accordance with the invention is prepared by attaching to a fiber a microcapsule containing and sealing therein 10% by weight or more of one or plural ones in mixture as selected from xcex1-hydroxy acids by using chitosan as crosslinking agent, wherein the clothing is composed such that the microcapsule and chitosan are at a weight ratio within a range of from about 4:1 to about 1:6, and the total amount of both of the two attached occupies from about 0.1 to about 15% of the fiber weight at dry state in the attached portion. Additionally, inorganic porous materials are preferably used as the wall material of the microcapsule.
The method for attaching the microcapsule in accordance with the invention comprises pouring and immersing a dispersion solution containing from about 4 to about 20% by weight of the microcapsule and at least 4 to about 30% by weight of chitosan and being adjusted of the initial pH within a range of from about 6.0 to about 7.0 in a process bath charged with a fabric, for immersion, thereafter raising the temperature of the process bath charged with the dispersion solution up to from about 40 to about 55xc2x0 C. as the upper limit and retaining the upper limit temperature to cany out absolute absorption process.
Briefly stated, the present invention relates to a clothing with effects on the reduction of skin dryness, skin roughness, wrinkle and spot, together with a method for attaching a microcapsule. The metabolism of keratin layer is promoted by using a clothing prepared by attaching to the fiber, a microcapsule containing and sealing therein at least 10% by weight of at least one xcex1-hydroxy acid. Chitosan is used as a crosslinking agent. The microcapsule and chitosan are given within a range of from about 4:1 to about 1:6 in weight ratio. The total amount of the chitosan and the microcapsule occupies from about 0.1 to about 15% of the fiber weight at a dry state.
According to an embodiment of the present invention, there is provided a clothing comprising: a fiber having a microcapsule containing and sealing therein at least about 10% by weight of at least one xcex1-hydroxy acid, by using chitosan as a crosslinking agent thereby improving the state of bare skin through the promotion of the metabolism of keratin layer; the microcapsule and the chitosan being present within a range of from about 4:1 to about 1:6 in weight ratio; and a total amount of the microcapsule and the chitosan occupying from about 0.1 to about 15% of the fiber weight at a dry state.
According to another embodiment of the present invention, there is provided a method for attaching a microcapsule to a fiber, comprising: forming a dispersion solution containing from about 4 to about 20% by weight of the microcapsule and at least 4 to about 30% by weight of chitosan; adjusting an initial pH of the dispersion within a range of from about 6.0 to about 7.0; immersing the fabric into a process bath; pouring the dispersion in the process bath; adjusting the temperature of the process bath charged with the dispersion solution up to a range from about 40 to about 55xc2x0 C.; and maintaining the temperature to carry out absolute absorption of the microcapsule onto the fiber.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.